Composition comprising an oxidizing and complexing compound

ABSTRACT

The present invention is related to a composition comprising an oxidizing compound and a complexing compound with the chemical formula wherein R1, R2, R3 and R4 are selected from the group consisting of H and any organic side chain. The oxidizing compound can be in the form of an aqueous solution. The complexing compound is for complexing metal ions. Metal ions can be present in the solution or in an external medium being contacted with the solution. The present invention can be used for cleaning a semiconductor substrate

This application is the national phase under 35 U.S.C. §371 of prior PCTInternational Application No. PCT/BE01/00219 which has an Internationalfiling date of Dec. 21, 2001, which designated the United States ofAmerica, and which was published by the International Bureau in Englishon Jul. 4, 2002, and which claims the benefit of U.S. ProvisionalApplication No. 60/257,928 filed Dec. 22, 2000.

FIELD OF THE INVENTION

This invention is situated in the field of products and methods for thestabilizing a composition comprising an oxidizing compound.

STATE OF THE ART

Chemical solutions comprising an oxidizing compound such as hydrogenperoxide are used in a wide area of applications, for example, asbleaching agent for paper pulp applications, dental bleachingcomposition or as cleaning agents.

Chemical solutions comprising an oxidizing compound have often problemsrelated to the stability of the solution. In pure form, aqueous solutionare stable over extended periods of time. However, the presence ofcertain metal ions in the solution causes decomposition of the oxidizingcompound. Consequently, stabilizers to prevent such decomposition shouldbe added. Stabilizers can be e.g. a complexing compound, such that thecomplexing compound will bind to the metal and consequently, the metalis not available for reaction with the oxidizing compound. Thus, thedecomposition of the oxidizing compound is substantially inhibited andthe lifetime of the solution is increased.

Very stringent specifications must be met by oxidizing solutions forspecialized applications such as semiconductor applications or reagentchemicals.

An overview of stabilizing oxidizing compound, and more specificallyhydrogen peroxide solutions, is given in Kirk-Othmer Encyclopedia ofChemical Technology (4^(th) edition), vol. 13 p. 965.

U.S. Pat. No. 4,239,643 discloses an aqueous peroxide-containingsolutions used in bleaching of cellulose fiber, wherein the stability ofthe peroxide is very greatly increased by inclusion of alkali metalpolyphosphate and alkali metal diethylene triamine penta(methylenephosphonate).

U.S. Pat. No. 3,903,244 describes a hydrogen peroxide concentratecontaining up to 50% hydrogen peroxide, 1 to 3% of a solubleamino(methyl phosphonic acid) or a salt thereof, and 0.05 to 0.5% ofphenol. The concentrate is useful in the preparation of highly acidmetal pickling baths.

Stabilizing compounds are useful for a wide area of application, such assoil remediation, metal etch bath, denture bleaching, bleaching of fats,oils, waxes,, wastewater treatment, paper pulp bleaching, textilebleaching, CMP applications or semiconductor applications. In cleaningapplication, for example in semiconductor application, oxidizingsolutions have been investigated extensively.

Since the invention of the RCA cleaning by Kern et al. in 1965 (W. Kernand D. A. Pautinen, RCA Review 31, 187, 1970) this cleaning cycle hasbecome the most used for semiconductors. The conventional RCA cleaningconsists of two steps: an alkaline solution, the so called SC1 solutionand an acidic solution, SC2. The SC1 solution is composed of 1 partammonia (NH₄OH), 1 part hydrogen peroxide (H₂O₂) and 5 parts ultra purewater (H₂O) and is often referred to as APM-cleaning (i.e. AmmoniaPeroxide Mixture). Originally it was used to remove organic residues byoxidation. Later it has been proven to be very efficient to removeparticles.

A drawback of the SC1 solution is that metals precipitate on siliconsurfaces; especially aluminum, iron and zinc have been shown to adsorbstrongly on the wafer surface (Mertens et al., Proc. of the 8^(th)Internat. Symp. On Silicon Materials Science and Technology PV98-1(1998)). In addition, especially Fe and Cu are found to catalyze thedecomposition reaction of the peroxide (Mertens et al., Proc. of the5^(th) Internat. Symp. on Cleaning Technology in Semiconductor DeviceManufacturing PV97-35 (1997)) leading to a decrease in the bathlifetime. In order to remove the metallic surface contamination, the SC2solution consisting of 1 part hydrochloric acid, 1 part hydrogenperoxide and 6 parts ultra-pure water is used. However, it is expensiveto get hydrochloric acid of sufficient quality for the usage in SC2solution. There is also a risk of re-contaminating the surface withparticles. Problems also occur in spray tools due the corrosive behaviorof hydrochloric acid.

With the progress in semiconductor manufacturing the requirementsconcerning particle and metal contamination as well as roughness of thesilicon surfaces became more stringent. This led to a number ofvariations of the RCA clean.

The potential problems related to the SC2 and the consideration toreduce process time and equipment by leaving out this acidic step led tothe development of single-stage cleaning procedures. This can be done byusing chemicals with reduced amount of metallic impurities. For thatpurpose, advanced purification procedures are established for obtainingultra-pure water, ammonia and hydrogen peroxide. However, thesechemicals are very expensive and the purity is not always assured whenthey are used in a cleaning bath. Moreover, the cleaning solution is notvery robust with respect to metal contamination from the semiconductorsubstrate and from the hardware.

Besides this, having an extra step in the cleaning cycle to removeresidual metallic contamination implies extra hardware, e.g. a SC2-tankand a rinse tank need to be used, and more chemicals. Leaving out thisextra step will results in a reduction of the hardware cost and areduction of the amount of chemicals used in the cleaning cycle.

EP 528053 describes a method for treating a surface of a substrate witha surface treatment composition. The surface treatment compositioncomprises a liquid medium containing a complexing agent as a metaldeposition preventive. The surface treatment composition is improved byincorporating at least two complexing agents. A first complexing agentis preferably an aromatic hydrocarbon ring with at least an OH or O⁻group bonded to a carbon atom constituting the ring. A second complexingagent is compound having a donor atom, such as heterocyclic amines.Since this cleaning composition comprises two complexing agents,drawbacks such as higher cost and increased waste treatment areobserved. Moreover, aromatic hydrocarbons such as Tiron, Catecholderivatives are hazardous for the environment and for humans.

U.S. Pat. No. 5,290,361 and U.S. Pat. No. 5,302,311 describes an aqueoushydrogen peroxide solution further comprising a complexing compoundcontaining phosphonic acid groups and showing complexing ability.Cleaning solution comprising phosphonic acid goups are not effective inremoving or suppressing Al from the substrate. Moreover, enhanceddeposition of Cu has been measured. This makes the cleaning solutionsless suitable.

In the present invention, the problems related to removal of metals asmentioned in the prior art, are avoided.

AIMS OF THE INVENTION

It is an aim of the invention to provide a stable composition comprisingan oxidizing compound and a complexing compound.

It is a further aim of the invention to provide a new composition fortreating a surface which is stable and provokes less or no metalprecipitation on the surface.

Another aim of the invention is to provide a new cleaning solution.Another aim of the present invention is to provide an efficientAPM-cleaning solution having a good robustness with respect to metalcontamination.

A further aim is to provide a new single-step method for cleaningsemiconductor surfaces.

FIGURE CAPTIONS

FIG. 1 chemical structure of complexing molecules

FIG. 2 bath age (minutes) as function of the normalized H₂O₂concentration, 1=no complexing agent; 2=DEHP; 3=10×DEHP; 4=1=EMHP;5=10×1-EMHP; 6-DMHP and 7=10×DMHP.

SUMMARY OF THE INVENTION

In a first aspect of this invention, a composition is disclosedcomprising an oxidizing compound and a complexing compound with thechemical formula

wherein R1, R2, R3 and R4 are selected from the group consisting of Hand any organic side chain. The oxidizing compound can be in the form ofan aqueous solution. The complexing compound is for complexing metalions. Metal ions can be present in the solution or in an external mediumbeing contacted with the solution. Depending on the metal ion beingcomplexed, one or more complexing molecules/metal ion are required.

In an embodiment of this first aspect, said composition as recited inthe first aspect of this invention can further comprise an alkalinecompound.

In a further embodiment of this first aspect, said organic side chaincan comprise an aliphatic side chain, a heterocyclic side chain or anaromatic side chain.

In a further embodiment of the first aspect of this invention, R3 and R4can be hydrogen while R1 and R2 can be a functionalized aliphatic sidechain. Preferably, said complexing compound is one of the groupconsisting of DEHP, 1-EMHP, 2-EMHP, DMHP, PEPH, PMHP, ECMHP and ECEHP.

In a further embodiment of this first aspect, a solution as recited inthe first aspect of this invention is disclosed characterized in thatsaid oxidizing compound is hydrogen peroxide. Hydrogen peroxide will bestabilized by the addition of the complexing compound, such thatdecomposition is substantially inhibited.

In a further embodiment of this first aspect of the invention, acomposition as disclosed wherein said oxidizing compound is hydrogenperoxide.

In a further embodiment of this first aspect, a composition as recitedin the first embodiment of the first aspect of the invention isdisclosed wherein alkaline compound comprises an inorganic or organicbasic compound. Said alkaline compound can be ammonia or an organicamine, preferably an organic amine chosen from the group consisting oftetraalkylammoniumhydroxide, alkanolamine,choline(hydroxyltrialkylammoniumhydroxide) and guanidine compounds.

In a second aspect of this invention, a method for treating asemiconductor substrate is disclosed. Said semicondcutor substrate istreated with a composition comprising an aqueous solution of acomplexing compound with the chemical formula

wherein R1, R2, R3 and R4 are selected from the group consisting of Hand any organic side chain. Said composition can further comprise anoxidizing compound.

Said composition can be used for treating a substrate, such thatparticles are oxidized and metallic contamination is removed. Thecomplexing molecule is for complexing metallic residues being present onthe substrate and in the solution. Additionally, the lifetime of thesolution is increased since de decomposition of the oxidizing compoundis substantially inhibited. Said solution is particularly suitable forcleaning a semiconductor substrate. Said composition for cleaning asemiconductor substrate can be any composition described in the firstaspect of this invention.

In an embodiment of this second aspect of this invention, said R1, R2,R3 and R4 are selected from the group consisting of H and any organicside chain. Said organic side chain can comprise an aliphatic sidechain, a heterocyclic side chain or an aromatic side chain. In a furtherembodiment of this second aspect of the invention, R3 and R4 can behydrogen while R1 and R1 can be a functionalized aliphatic side chain.In a further embodiment, said complexing compound is one of the groupconsisting of DEHP, 1-EMHP, 2-EMHP, DMHP, PEPH, PMHP, ECMHP and ECEHP.

In another embodiment of the second aspect of the present invention,said oxidizing compound can be hydrogen peroxide.

In an embodiment of the second aspect of this invention, saidcomposition can further comprise an alkaline compound. Said alkalinecompound can comprise an inorganic or organic basic compound. Said basiccompound can be chosen from the group consisting of ammonia and organicamine, preferably an organic amine chosen from the group consisting oftetraalkylammoniumhydroxide, alkanolamine,choline(hydroxyltrialkylammoniumhydroxide) and guanidine compounds.

In an embodiment of the second aspect of this invention, the method asrecited in second aspect of the invention is disclosed wherein theconcentration of hydrogen peroxide in the solution lies between 0.001 to30 weight %.

In an embodiment of the second aspect of this invention, the method asrecited in second aspect of the invention is disclosed in which theamount of the complexing agent lies between 0.1 and 1000 ppm of saidsolution.

In an embodiment of the second aspect of this invention, the method asrecited in second aspect of the invention is disclosed wherein theamount of the alkaline compound lies between 0.001 and 30 weight %.

DETAILED DESCRIPTION OF THE INVENTION

In relation to the appended drawings the present invention is describedin detail in the sequel. It is apparent however that a person skilled inthe art can imagine several other equivalent embodiments or other waysof executing the present invention.

In an aspect of this invention, said composition comprises an oxidizingcompound and a complexing compound. Said oxidizing compound can be inthe form of an aqueous solution.

Said complexing agent can have a chemical formula as given in FIG. 1.R₁, R₂, R₃ and R₄ are independently selected from the group comprisinghydrogen (H) or any organic group. R₁, R₂, R₃,or R₄ can have a differentchemical structure. For the purpose of this invention, said complexingagent as mentioned above is generally referred to as pyridinone.

Said organic group can be every possible sequence of C, N, O or S atomslinked to each other by single, double or triple bonds such that thecomplexing properties of the final complexing agent are assured. Saidorganic group can be selected from the group comprising aliphatic sidechains, heterocycles and aromatic structures.

Said organic side chain is every possible sequence of carbon, atomslinked to each other by a single, double or triple bound and optionallycharacterised by the presence of functional groups linked to the carbonatoms. Functional groups can be alcohol, carboxyl, carbonyl, aldehyde,keton, ether, ester, amine, amide, halogen containing groups.

Said heterocycle can be one of the group comprising a crown ether, acryptant, a calixarene, . . . In a preferred embodiment, R₃ and R₄ are Hatoms, while R₁ and R₂ are a methyl, ethyl, (iso)propyl or butyl group.Said methyl, ethyl, (iso) propyl or butyl group can functionalized, e.g.with a carboxyl group (COOH or COO⁻). Preferably, the complexingmolecules as described in FIG. 2 are used.

-   DEHP=1,2-Diethyl-3-hydroxy-4(1H)-pyridinone-   1-EMHP=1-Ethyl-2-methyl-3-hydroxy-4(1H)-pyridinone-   2-EMHP=1-Methyl-2-ethyl-3-hydroxy-4(1H)-pyridinone-   DMHP=1,2-Dimethyl-3-hydroxy-4(1H)-pyridinone-   PEPH=1-Propyl-2-ethyl-3-hydroxy-4(1H)-pyridinone-   PMHP=1-Propyl-2-methyl-3-hydroxy-4(1H)-pyridinone-   ECMHP=1- (2′Carboxyethyl)-methyl-3-hydroxy-4(1H)-pyridinone-   ECEHP=1-(2′Carboxyethyl)-2-ethyl-3-hydroxy-4(1H)-pyridinone.

Although the addition of the amount of complexing agent in thecomposition in this invention is not particularly limited, it depends onthe degree of metal contamination -and on the kind of other compoundsbeing present in the solution. Furtheron, the amount of complexing agentdepends on the specific chemical structure of the complexing compound.The amount of the complexing agent lies 0.01 and 10000 ppm, between 0.1and 1000 ppm of said composition. For this application, ppm should beunderstood as parts per million in the composition.

The amount of complexing compound depends on the specific complexingcompound.

Since said complexing agents do not form a 1:1 metal/complexing agentcomplex, higher concentrations of complexing agents are required,compared to other complexing agents such as EDTA. Typical values for thestoichiometry CA/metal for Fe, Al, Cu and Zn are given in the table:

Complex Stability Constants:

Fe¹ Al² Cu Zn Fe² Al² Cu Zn² DMHP DMHP DMHP DMHP DEHP DEHP DEHP DEHP[ML]/[M] [L] 15.10 12.20 10.62 7.19 15.2 13.42 10.74 7.70 [ML₂]/[ML]11.51 11.05 8.99 6.34 11.76 11.64 9.07 6.09 [L] [ML₃]/[ML₂] 9.27 9.379.78 8.48 5.12 [L] [ML_(x)]/[M] 35.88 32.62 19.61 13.53 36.8 33.54 19.8118.91 [L]^(x) ² DMHP 1-EMHP DEHP [ML_(x)]/[M] 37.2/36.4 37.7 36.8[L]^(x) PFe 19.4 19.7 ¹X = 3 ²Values have been taken from differentauthors and determined by different techniques.

Said oxidizing compound can be every chemical compound having oxidizingproperties. E.g. organic species, metallic compounds, inorganicparticles, silicon, etc. can be oxidized.

The oxidizing compound is a compound selected from the group comprisinghydrogen peroxide or oxidizing anions. The oxidizing anions can be e.g.nitric acid and its salts, nitrate, persulfate, periodate, perbromate,perchlorate, iodate, bromate and chlorate salts of ammonium. Preferably,the oxidizing compound is hydrogen peroxide.

The concentration of the oxidizing compound can be, but is not limitedhereto, between 0.0001 and 99 weight %, between 0.001 and 90 weight %and preferebly between 0.001 to 30 weight %.

In this application, weight % should be understood as the percentage ofweight of the specified compound in the composition.

Said composition can further comprise an alkaline compound. The alkalinecompound or base can be every chemical compound with a pH higher than 7.The alkaline compound can be an organic or inorganic compound. Thealkaline compound can be an organic base, ammonia, ammoniumhydroxide, oran alkaline solution containing metal ions such as potassium or sodium.Said organic base can be a quaternary ammonium hydroxide such astetraalkyl ammonium hydroxide in which the alkyl groups can containhydroxy- and alkoxy-containing groups with 1 to 4 carbon atoms in thealkyl or alkoxy group. Said organic base can further be an organic aminesuch as an alkanol amine. Alkanol amines can be 2-aminoethanol, 1-amino2-propanol, 1-amino 3-propanol. Preferably, the alkaline compounds aretetramethyl ammonium hydroxide, and trimethyl 2-hydroxy ethyl ammoniumhydroxide (choline) and ammonium hydroxide. The amount of the alkalinecompound lies between 0.0001 and 90 weight %, between 0.001 and 50weight %, between 0.001 and 30 weight %.

Said composiiton can further comprise a surfactant.

In a second aspect of this invention, a method for treating asemiconductor substrate is disclosed. Said semiconductor substrate istreated with a composition comprising an aqueous solution of acomplexing compound with the chemical formula

wherein R1, R2, R3 and R4 are selected from the group consisting of Hand any organic side chain. Said composition can further comprise anoxidizing compound.

Said composition can be, but is not limited hereto, the compositiondescribed in the first aspect of this invention. Said composition isparticularly usefull for cleaning a substrate such that particles areoxidized and metallic contamination is removed. The complexing compoundis for complexing metals being present on the substrate and in thesolution. Additionally, the lifetime of the solution is increased sincede decomposition of the oxidizing compound is substantially inhibited.

A substrate can be, but is not limited hereto, a substrate such assemiconducting material, glass, quartz, ceramics, metal, plastic,magnetic material, superconductor and the like.

Preferably, said substrate is a semiconductor substrate. Semiconductorsubstrate can be every possible substrate used in semiconductorprocessing. Said semiconductor substrate can be a substrate selectedfrom the group, but not limited hereto, comprising a substrate made ofsilicon, germanium, gallium arsenide, indium phosphide, etc.

The semiconductor substrate be e.g. the substrates as mentioned abovecovered entirely op partially with a thin film of e.g. an oxide, anitride, a metal, a polymeric insulating layer, an anti-reflectingcoating, a barrier, a photoresist layer, etc.

The present invention is particularly relevant for cleaning or etching asemiconductor substrate of which the surface should be highly clean.

When the composition is used for treating a substrate, the weightconcentration range of the alkaline compound in the-cleaning solutionare typically but not limited to 0.001–100%, 0.1–20% and preferably0.1–5% by weight.

For ammonium hydroxide, the weight concentration range of the alkalinecompound in the cleaning solution are typically but not limited to0.001–30%, 0.1–20% and preferably 0.1–5% by weight. For other alkalinecompounds, the weight concentration range is equivalent, and function ofthe strength of the alkaline compound.

For peroxide, the weight concentration the hydrogenperoxide is typicallybut not limited to 0.001–100%, 0.1–20% and preferably 0.1–5% by weight.

In the preferred embodiment of this invention, a composition fortreating a semiconductor surface comprises ammonium hydroxide, hydrogenperoxide, water (hereafter called APM mictures) and additionally acomplexing agent. Said complexing agent is one of the group consistingof the molecules as described in FIG. 2.

APM-cleaning mixtures comprising a complexing agent according to thepresent invention are robust with respect to metal contamination comingfrom the fresh chemicals as well as with respect to metal contaminationintroduced in the course of its use for cleaning. The robustness of thebasic APM process can be improved by the addition of complexing agentswhich keep the metals in solution and prevent the above mentionedcatalysis of the peroxide decomposition.

The volume mixing ratio of NH₄OH(29%)/H₂O₂(30%)/H₂O is typically, butnot limited hereto, 0.25/1/5.

The cleaning solution is prepared with the amounts as described aboveand afterwards the semiconductor substrate is treated with the cleaningsolution.

In the best mode known to the applicant, molecule DMHP is selected andadded in the amounts described above. The complexing agent can be addedas the pure compound to the cleaning solution. Alternatively, thecomplexing agent can be dissolved in either water, ammonia or peroxideor a dilution of the two latter chemicals and added as such to thecleaning solution.

It is a further aim of the invention to disclose a process for treatinga semiconductor substrate comprising the steps of

-   treating said semiconductor substrate with the cleaning solution as    described above and drying said semiconductor substrate.

An optional step: rinsing said semiconductor substrate can be performedafter said treating said semiconductor substrate with the cleaningsolution as described above.

In the step of treating said semiconductor substrate with said cleaningsolution, the semiconductor substrate can be immersed in a bathcontaining the cleaning solution. Alternatively, the cleaning solutioncan be dispensed or sprayed onto the semiconductor substrate forinstance by using a spray processor. In all cases, the cleaningperformance of the solution can be enhanced by using a megasonictransducer.

The temperature range for treating the semiconductor substrate with thecleaning solution is typically but not limited to 0–95 degrees Celcius,10–80 degrees Celcius and preferably between 20–70 degrees Celcius.

In the step of drying the semiconductor substrate, several techniquesknown in the art can be used, e.g. spin-drying, Maragoni-drying, dryingtechniques using organic vapours.

The step of rinsing the semiconductor substrate comprises treating thesemiconductor substrate with DI water or treating the semiconductorsubstrate with a diluted acidic solution or with DI water containing thecomplexing agent in an amount of 1 to 100000 ppm, 10 to 10000 ppm and bypreference 100 to 1000 ppm.

It is a further aim of the invention to describe a process for treatinga semiconductor substrate comprising the step of:

-   treating said semiconductor substrate with any cleaning solution    and/or-   treating said semiconductor substrate with any rinsing solution

Said any cleaning solution can be any cleaning solution, not beinglimited to the compositions described in this application. Said rinsingsolution comprises said complexing agent and water. Said complexingagent can be any complexing agent described in this application. Theamount of the complexing agent in the composition can be between 1 and100000 ppm, 10 and 10000 ppm and by preference between 100 and 1000 ppm.

This rinsing solution can also comprise a surfactant in an amount of 0.1ppm to 10 w %.

A surfactant is a surface-active agent comprising a lyophobic group anda lyophilic group. The lyophobic group can be a straight-chain alkylgroup or a branched-chain alkyl group (C8–C20), an long-chain (C8–C20)alkyl benzene residue, an alkylnaphtalene residue (C3 and greater-lengthalkyl groups), high-molecular-weight propylene oxide polymers(polyoxypropylene glycol derivatives), long-chain perfluoroalkyl orpolysiloxane groups.

Depending upon the lyophilic group, the surfactant can be an anionic,cationic, nonionic or zwitterionic surfactant. Anionic surfactants canbe carboxylic acids or carboxylic acid salts (such as sodium andpotassium salts of straight-chain fatty acids), sulfonic acids orsulfonic acid salts (such as linear alkylbenzenesulfonates, higheralkylbenzenesulfonates, benzene-, toluene-, xylene- andcumenesulfonates, ligninsulfonates, petroleum sulfonates,N-acyl-n-alkyltaureates, paraffin sulfonates, secondaryn-alkanesulfonates, α-olefin sulfonates, sulfosuccinate esters,alkylnaphtalenesulfonates or isethionates), sulfuric acid ester salts(such as sulfated linear primary alcohols, sulfated polyoxyethylenatedstraight-chain alcohols or sulfated triglyceride oils), phosphoric andpolyphosphoric acid esters. Cationic surfactants can be primary aminesand their salts, diamines and polyamines and their salts, quaternaryammonium salts (such as tetralkylammonium salts or imidazolinium salts),polyoxyethylenated long-chain amines (RN(CH₂CH₂O)_(x)H]₂), quaternizedpolyoxyethylenated long-chain amines or amine oxides (such asN-alkyldimethylamine oxides). Nonionic surfactants can bepolyoxyethylenated alkylphenols, polyoxyethylenated straight-chainalcohols, polyoxyethylenated polyoxypropylene glycols,polyoxyethylenated mercaptans, long-chain carboxylic acid esters (suchas glyceryl and polyglyceryl esters of natural fatty acids, propyleneglycol, sorbitol or polyoxyethylenated sorbitol esters, polyoxyethyleneglycol esters and polyoxyethylenated fatty acids), alkanolamides,tertiary acetylenic glycols, polyoxyethylenated silicones,N-alkylpyrrolidones or alkylpolyglycosides. Zwitterionic surfactantshave both anionic and cationic charges present in the lyophilic portion(such as β-N-alkylaminopropionic acids, N-alkyl-β-iminodipropionicacids, imidazoline carboxylates, N-alkylbetaines, amine oxides,sulfobetaines or sultaines) (M. J. Rosen, Surfactants and Interfacialphenomena, 2^(nd) Edition, John Wiley and Sons, New York, 1989])

No additional alkaline compound should need to be added to the saidrinsing solution. The pH range of said rinsing solution can typicallybe, but not limited to, between 5 and 8. Said Rinse solution can bedispensed or sprayed onto the semiconductor surface as described above.During rinsing the performance can also be enhanced by using a megasonictransducer.

The process of treating a semiconductor substrate with a cleaningsolution comprising the above mentioned steps can be performed for acertain number of semiconductor substrates. After treating at least onesubstrate, but preferably after treating more substrates, thecomposition of the cleaning solution can be modified by e.g. addingextra alkaline compound, adding extra complexing compound, addingoxidizing compound such that the initial composition of the cleaningsolution is kept constant as function of the process time.

COMPARATIVE EXAMPLES

The present invention will be further described using non-limitingexamples and drawings.

The effectiveness of the new class of complexing agents on theinhibition of the metal catalyzed decomposition of peroxide and theprevention of metal outplating on silicon wafers in metal contaminatedAPM cleaning solutions is described next. For complexing agents asdisclosed in this invention, different model compounds are selected(1-EMHP, 2-EMHP, DMHP, DEHP, PEHP, PMHP, ECMHP and ECEHP) and added tothe bath at a concentration of 2.67×10⁻⁵ M and at a 10×, 40×, or 50×higher concentration (namely 2.65×10⁻⁴ 10.6×10⁻⁴ and 13.25×10⁻⁴ M). Acomparison is made with other types of complexing agents containing asfunctional groups either phosphonic acids, such as diethylene (kleineletter) triamine penta-methylenephosphonic acid (DTPMP), carboxylicacids, such as ethylene diamino tetra acetic acid (EDTA). An overview ofthe different chemicals used for the experiments is given in Table 1.All experiments were done in a class 1000 clean room environment orbetter.

TABLE 1 Chemicals used for preparation of APM baths. Chemical VendorGrade H₂O₂ 30 (w/w) % Ashland TB(*) NH₄OH 29 (w/w) % Ashland TB(*) EDTAFluka DTPMP Monsanto Dequest 2060S DMHP Aldrich (*)TB-grade correspondswith a specification of maximal 100 ppt of metal ions in the chemical.

Example 1 Metal Outplating from APM Mixtures in Presence of DifferentComplexing Agents

The efficiency of complexing agents to suppress the deposition ofmetallic contamination onto wafer surfaces was studied. This was donethrough intentionally spiking well controlled trace amounts of metalliccontamination to cleaning solutions. For these metal deposition tests,p-type monitor wafers with a diameter of 150 mm and <100> orientationwere used. The wafers were pre-cleaned using IMEC Clean® in an automatedSteag wet bench (i.e. SOM+dHF+O₃-rinse rendering a perfectly cleanhydrophilic surface).

The metal deposition experiments were performed in a static quartz tankwith a quartz cover plate. This tank was not equipped with a megasonictransducer. APM mixtures were prepared containing 1 w-ppb of differentmetals of interest with/without the complexing agent added. The metalsspiked to the APM bath were added from AAS-standard solutions (Merck).After a bath age of 5 minutes, three wafers were immersed for 10minutes, rinsed for 10 minutes in an overflow rinse tank and dried witha commercially available Marangoni drier (STEAG). The resulting metalcontamination was measured with straight TXRF or VPD-DSE-DC-TXRF (VaporPhase Decomposition Droplet Surface Etching Droplet Collection TotalX-Ray Fluorescence). Determination of Al water surface concentration wasdone using VPD-DC GF-AAS (Graphite Furnace Atomic AbsorptionSpectroscopy).

An overview of the resulting metal surface contamination after dipping aclean wafer in an APM spiked with metals and different complexing agentsis given in Table 2.

TABLE 2 Measured metal surface concentrations after immersion in metalcontaminated 0.25/1/5 APM solution at 20–50° C. with differentcomplexing agents present. Complexing Conc. CA Conc. Mt Al (10¹⁰ Feagent (2.7 × 10⁻⁵ M) (w-ppb) at/cm²) (10¹⁰ at/cm²) Pre-clean only NA NA2.34 <DL None 0 0 39.3 ± 6   1.5 ± 0.4 None 0 1 360 ± 21  109 ± 14  EDTA1 1 NM 25.1 ± 0.1  10 1 272 ± 16  NM 100 1 274 2.78 EDTA + 1 + 2 1 257 ±2  <DL DTPMP 1-EMHP (1) 1 1 356 ± 32  0.51 ± 0.02 10 1 142 ± 68  0.231-EMHP (2) 1 1 292 ± 1  0.20 ± 0.00 10 1 27 ± 33 NA 50 1 0.5 ± 0.2 0.262.4 ± 1.4 0.16 2-EMHP 1 1 404 0.35 ± 0.01 10 1 248 ± 69  0.22 50 1 0.8 ±0.2 0.15 DEHP 1 1 369 ± 0  0.33 ± 0.01 10 1 150 ± 41  0.92 50 1 2.6 ±0.6 0.15 DMHP 1 1 392 ± 0  0.45 ± 0.01 (Aldrich) 10 1 101 ± 2  0.21 50 11.2 ± 0.1 NM DMHP 1 1 387 ± 0  0.40 ± 0.02 10 1 230 ± 5  0.18 PEHP 40 14.6 ± 0.2 0.14 ± 0.0  PMHP 40 1 1.13 0.14 ± 0.14 ECMHP 40 1 15.0 ± 0.5 0.08 ± 0.04 ECEHP 40 1 14.2 ± 1.7  0.15 ± 0.05

These data show that the addition of EDTA results in a decrease of thefinal Fe contamination levels but has no effect on the reduction of Alcontamination. The use of DTPMP in a 1 w-ppb metal spiked bath, is veryefficient to reduce the final Fe surface concentration but has no effecton suppression of Al deposition.

The new class of pyridinone complexing agents are able to reduce thefinal Fe and Al surface concentration on the wafer. Higherconcentrations of complexing agent are needed because the pyridones donot form a 1:1 metal/chelate complex. When using the pyridinones at aconcentration of 13.25×10⁻⁴ M in the bath, the resulting Fe and Alsurface contamination levels are below the values measured on a wafertreated with a clean, i.e. no metals spiked, APM solution.

Example 2 Decomposition of Peroxide in APM Cleaning Mixtures in Presenceof Trace Metal Contamination and Metal Complexing Agents

The effect of the addition of a complexing agent to APM cleaningsolutions on the kinetics of the decomposition reaction of H₂O₂ has beeninvestigated. Well controlled amounts of metallic contamination wereadded to the cleaning mixture under study.

As hydrogen peroxide decomposes, an amount of oxygen gas is liberatedfollowing the overall reaction2 H₂O₂⇄O₂+2 H₂O

The decay of the total peroxide concentration in the APM mixture can bemonitored by measuring the time-dependent increase of the pressure dueto the O₂-evolution in a dedicated set-up as described by Schmidt.

Numerical integration over time yields the actual peroxide concentrationin the bath. It is convenient to use peroxide concentrations normalizedto its initial value [H₂O₂]_(i) as

$\left\lbrack {H_{2}\; O_{2}} \right\rbrack_{n} = \frac{\left\lbrack {H_{2}\; O_{2}} \right\rbrack}{\left\lbrack {H_{2}\; O_{2}} \right\rbrack_{i}}$

Since the decomposition reaction is mainly catalyzed by Fe and in alesser content Cu (Mertens et al. Proc. of the 5^(th) Internat. Symp. onCleaning Technology in Semiconductor Device Manufacturing PV97-35(1997), the decay of peroxide concentration in a metal contaminated bathand in presence of a CA, illustrates the ability of complexing primarilyFe in the APM bath.

The decomposition rate as function of bath age is determined in APMmixtures (0.25/1/5 29%NH₄OH/30% H₂O₂/H₂O) spiked with 1 w-ppb of themetals of interest with and without different complexing agents. Theeffect of different additives on the inhibition of the metal catalyzeddecomposition reaction of peroxide in APM cleaning mixtures is shown inFIG. 2. This graph shows the normalized H₂O₂ concentration as functionof bath age for an APM mixture at 50° C. spiked with differentcomplexing agents and the metals of interest.

All complexing agents are found to suppress to some extent thedecomposition reaction, at least when the mixture is fresh. For some CA,the suppression action vanishes over time. This may be attributed to thedestruction of the complexing agent or more specifically of themetal-complex in the hot APM. The time over which they remain active incomplexing metals is summarized in Table 3 and can be used to establishthe effective lifetime.

In example 1 it was demonstrated that higher CA concentrations have tobe used in the cleaning solution. FIG. 1 and Table 3 show that withincreasing complexing agent concentration, the effective lifetime of thebath can be increased substantially. Increasing the complexing agentconcentration even further would result in a more prolonged lifetime.

TABLE 3 Effective lifetime of complexing agents in 0.25/1/5 metal spikedAPM-cleaning mixtures at 50° C. Conc. CA Effective lifetime Complexingagent (2.7 × 10⁻⁵ M) (min) None 0 40 DEHP 1 40 10 120 1-EMHP (1) 1 40 1050 1-EMHP (2) 1 60 10 90 2-EMHP 1 30 10 40 DMHP FfU 1 40 10 100 DMHPAldrich 1 20 10 60

1. A composition comprising an aqueous solution, said aqueous solutioncomprising an oxidizing compound and a complexing compound, saidcomplexing compound comprising a chemical formula

wherein R1, R2, R3, and R4 are each independently selected from thegroup consisting of H and an organic side chain.
 2. The composition asrecited in claim 1, further comprising an alkaline compound.
 3. Thecomposition as recited in claim 1, wherein said organic side chain isselected from the group consisting of an aliphatic side chain, aheterocyclic side chain, and an aromatic side chain.
 4. The compositionas recited in claim 1, wherein R3 and R4 each comprise hydrogen and R1and R2 each comprise a functionalized aliphatic side chain.
 5. Thecomposition as recited in claim 1, wherein said complexing compound isselected from the group consisting of1,2-diethyl-3-hydroxy-4(1H)-pyridinone,1-ethyl-2-methyl-3-hydroxy-4(1H)-pyridinone,1-methyl-2-ethyl-3-hydroxy-4(1H)-pyridinone,1,2-dimethyl-3-hydroxy-4(1H)pyridinone,1-propyl-2-ethyl-3-hydroxy-4(1H)-pyridinone,1-propyl-2-methyl-3-hydroxy-4(1H)-pyridinone,1-(2-carboxyethyl)-2-methyl-3-hydroxy-4(1H)-pyridinone, and1-(2-carboxyethyl)-2-ethyl-3-hydroxy-4(1H)-pyridinone.
 6. Thecomposition as recited in claim 1, wherein said oxidizing compoundcomprises hydrogen peroxide.
 7. The composition as recited in recited inclaim 2, wherein said alkaline compound comprises an inorganic basiccompound or an organic basic compound.
 8. The composition as recited inclaim 7, wherein said alkaline compound is selected from the groupconsisting of ammonia and organic amine compounds.
 9. The composition asrecited in claim 2, wherein an amount of oxidizing compound comprisesfrom 0.001 to 30 weight %.
 10. The composition as recited in claim 1,wherein an amount of the complexing agent comprises from 0.1 to 1000 ppmof said solution.
 11. The composition as recited in claim 7, wherein anamount of the inorganic basic compound or the organic basic compoundcomprises from 0.001 to 30 weight %.
 12. The composition as recited inclaim 1, wherein an amount of said oxidizing compound comprises from0.001 to 95 weight %.
 13. A method of treating a semiconductorsubstrate, wherein said method comprises treating a semiconductorsubstrate with a composition comprising an aqueous solution, saidaqueous solution comprising a complexing compound comprising thechemical formula

wherein R1, R2, R3, and R4 are each independently selected from thegroup consisting of H and an organic side chain.
 14. The method asrecited in claim 13, wherein said composition further comprises anoxidizing compound.
 15. The method as recited in claim 13, wherein saidcomposition further comprises an alkaline compound.
 16. The method asrecited in claim 13, wherein said organic side chain is selected fromthe group consisting of an aliphatic side chain, a heterocyclic sidechain, and an aromatic side chain.
 17. The method as recited in claim13, wherein R3 and R4 each comprise hydrogen and R1 and R2 each comprisea functionalized aliphatic side chain.
 18. The method as recited inclaim 13, wherein said complexing compound is selected from the groupconsisting of 1,2-diethyl-3-hydroxy-4(1H)-pyridinone,1-ethyl-2-methyl-3-hydroxy-4(1H)-pyridinone,1-methyl-2-ethyl-3-hydroxy-4(1H)-pyridinone,1,2-dimethyl-3-hydroxy-4(1H)pyridinone,1-propyl-2-ethyl-3-hydroxy-4(1H)-pyridinone,1-propyl-2-methyl-3-hydroxy-4(1H)-pyridinone,1-(2-carboxyethyl)-2-methyl-3-hydroxy-4(1H)-pyridinone, and1-(2-carboxyethyl)-2-ethyl-3-hydroxy-4(1H)-pyridinone.
 19. The method asrecited in claim 14, wherein said oxidizing compound comprises hydrogenperoxide.
 20. The method as recited in claim 15, wherein the alkalinecompound comprises an inorganic basic compound or an organic basiccompound.
 21. The method as recited in claim 20, wherein said inorganicbasic compound or said organic basic compound is selected from the groupconsisting of ammonia and organic amine compounds.
 22. The method asrecited in claim 14, wherein an amount of the oxidizing compoundcomprises from 0.001 to 30 weight %.
 23. The method as recited in claim15, wherein an amount of the alkaline compound comprises from 0.001 to30 weight %.
 24. The method as recited in claim 13, wherein an amount ofsaid complexing compound comprises from 0.1 ppm to 1000 ppm.
 25. Thecomposition as recited in claim 8, wherein said organic amine isselected from the group consisting of tetraalkylammoniumhydroxidecompounds, alkanolamine compounds,choline(hydroxyltrialkylammoniumhydroxide) compounds, and guanidinecompounds.
 26. The method as recited in claim 21, wherein said organicamine is selected from the group consisting oftetraalkylammoniumhydroxide compounds, alkanolamine compounds,choline(hydroxyltrialkylammoniumhydroxide) compounds, and guanidinecompounds.
 27. A method of etching a metal, wherein said methodcomprises etching the metal in a metal etch bath comprising an aqueoussolution, said aqueous solution comprising a complexing compoundcomprising the chemical formula

wherein R1, R2, R3, and R4 are each independently selected from thegroup consisting of H and an organic side chain.